# 6.1 eliminated antenna DB Gain with transmit power

6.1 eliminated the antenna DB Gain setting and replaced it with a new transmit power setting. It defaults to 30 dbm.

What should the power setting be on a 9000apf with the built in 12db antenna and band pass filter?

Do I use the default setting or should it be some thing else?

The description of this change does not appear to be in the release notes.

The value that goes in the box is the Maximum Transmit Power that the operator wants the unit to transmit in dBm.

So as an example with 900 MHz here in the US the maximum transmit power allowed is 4 watts or 36 dBm, but you have to take into account the antenna gain and cable loss of the coax pigtail. Therefore, the customer would take 36 dBm - 9 dBi (cable loss for our unit is minimal) which equals 27 dBm and that is what gets entered into the configuration screen.

If you want the maximum power output to be 3 watts then the equation would look like 35 dBm - 9 dBi = 26 dBm

At quick table of watt to dBm conversion:

4 watts = 36 dBm
3 watts = 35 dBm
2 watts = 33 dBm
1 watt = 30 dBm
.5 watts = 27 dBm
.1 watts = 20 dBm

Does this help?

Based on information I received today the integrated bandpass filter in the 9000APF creates a 1db loss. So if I understand the process I should set the power output to 25 for the 9000APF with the integrate 12db antenna and bandpass filter. Can you confirm this?

Concerning your statement about the loss on the cables being minor. If the loss is .19db per foot, which I’m guessing the cable is, then 3 feet of cable with the connector is going to equal about .6db of loss or about 12% loss on a 4W EIRP radio. I don’t believe this is minor. Can you tell me what the exact loss is on your cable for the connectorized version?

Thanks, I do appreciate the response.

How did you calculate 12% loss? That is extremely high and incorrect.

It’s very possible my calculations are incorrect. Of course I don’t know what the exact loss per foot the cables used on the connectorized version introduce, so I am guessing.

Using the Radio Mobile program and setting up an antenna with a 9db gain and a radio with 27dbm of output I get 3.98W of EIRP. If I introduce .6 db of loss for the cable and connector without changing the power output or antenna gain I get 3.47W of EIRP.

3.47 is 87% of 3.98 leaving me with 13% loss.

I realize you can up the power to a maximum of 28 and also install a different antenna with higher gain. But given these two devices, the above guess at the cable loss plus the loss associated with an external band pass filter (best I have found is .5db of loss) then the output drops to 3.09W of EIRP. Even jumping the power to 28 (the maximum) only increases the output to 3.89W of EIRP. Still less than the 3.98W of legal output.

I really would like to know where the calculations above are wrong. I am still learning and am always interested in where the logic goes wrong.

Thanks.